His tweet came hours after the Financial Times reported that Saudi Arabia’s sovereign wealth fund had built a significant stake in Tesla, but it was unclear if that was the funding Mr Musk was referring to.

The Financial Times said Saudi Arabia’s Public Investment Fund had built a stake of between 3-5% of Telsa’s shares.

Tesla did not immediate respond to requests for comment.

The company’s shares were up more than 5% at more than $360 (£278).

It is highly unusual for the head of a major company make a significant announcement in such casual manner.

The tweet prompted questions about how serious Mr Musk’s intentions were. His asking price of $420 would be up 22% of Monday’s closing share price, and nearly 9% above the stock’s all-time closing high of $385.

The figure even drew some jokes on Twitter about whether it was a pot reference, with 420 being a common slang term for marijuana.

Mr Musk’s tweet came two weeks after Tesla revealed it had burned through $739.5 (£571m) million in cash on its way to a record $717.5 (£554m) million net loss in the second quarter, as it cranked out more electric cars.

Tesla has spent millions as it reached a goal of producing 5,000 Model 3 sedans per week by the end of June.

The company says production is rising, with the goal of 6,000 per week by the end of August.

Mr Musk pledged earlier this month to post net profits in future quarters, and he said he expects the company to avoid returning to the markets for capital and to be self-funding going forward.